The present invention relates to an antitheft device for the construction machinery and, more specifically, to an antitheft device for preventing any attempt of thieving a vehicle of construction machinery equipped with an engine and hydraulic control unit.
As an antitheft device for a construction machine such as hydraulic shovel, bulldozer, etc., a key switch is provided in a circuit that connects a starter motor in the engine starter circuit to a battery. The key switch has, for example, an engine key of a pattern different for every machine, and the circuit is allowed to flow the electric current by using the engine key. Therefore, the key switch can be operated by using a predetermined engine key only to actuate the starter motor so as to start the engine. Thus, the machine is prevented from being thieved by a person who attempts to thieve the construction machine without having a right engine key.
The antitheft device for the construction machinery of the above-mentioned conventional form has problems that must be solved as described below. That is, a person who intends to thieve the construction machine modifies the key switch part in the engine starter circuit to connect the circuit to establish its function, and feeds the electric power from the battery to the starter motor so as to start the engine. If the circuit is connected, the machine controller that controls the operation of the engine and of the working unit is actuated to enable the machine to move and hence, it is no longer possible to prevent the attempt to thieve the machine.
The present invention was pursued in view of the above-mentioned fact, and its technical subject is to provide an antitheft device for the construction machinery, which reliably makes it impossible to start the engine and to actuate the hydraulic control unit even though the starter circuit of the engine of the construction machine is modified.
In the present invention, as an antitheft device for the construction machinery, which solves the above-mentioned technical subject, there is provided an antitheft device for the construction machinery having an engine, a hydraulic control unit and a machine controller for controlling the engine and the hydraulic control unit, wherein the initial state of the machine controller is so set that the fuel injection by a fuel injection unit of the engine is halted and that the operations of control units in the hydraulic control unit are halted; and an antitheft control unit is provided and the initial state of the machine controller is released upon receiving a release signal from the antitheft control unit.
Further, it is not permitted to operate to start the engine actuate the hydraulic control unit unless a release signal is input to the machine controller from the antitheft control unit.
In a preferred embodiment, the antitheft control unit is connected to the machine controller through a communication circuit. Further, the antitheft control unit has an input unit through which a personal identification number is input as the release signal.
It is therefore made possible to reliably prevent the machine from being thieved by a person who attempts to thieve the machine, since the antitheft control unit is connected to the machine controller through the communication circuit, and the initial state (fuel injection into the engine is halted and operations of the hydraulic control units are halted) of the machine controller is released by the personal identification number.
In the present invention, the hydraulic control unit controls the workings of the hydraulic actuators of the operation units in the construction machinery, and the control units are hydraulic units such as directional control valve, pressure control valve and the like for the hydraulic control.